1. Field of the Invention
This invention relates generally to engine controllers and, more particularly, to the design of software programmable protected input circuits.
2. Description of the Related Art
Most present day internal combustion engines, or other type of automotive or general-purpose engines are controlled using engine control units (ECUs). Typically, an ECU is an electronic, oftentimes computerized or computer-directed control unit operated to read feedback values from a number of sensors situated within and around the engine (e.g. in the engine bay for vehicles), and interpret the feedback data using multidimensional performance maps and computational models, e.g. through various look-up tables. The ECU is further operated to control the engine according to the interpreted data by adjusting a series of actuators that are either functional parts of the engine or part of control circuitry also situated near the engine (again, for example in the engine bay for vehicles), to ensure optimum running and operation of the engine. Computerized ECUs can be programmable, which allows for efficiently adapting ECUs to different types of engines and/or in cases aftermarket modifications are made to an engine. Operations and/or characteristics that can be controlled by an ECU include air/fuel ratio for fuel injection engines, ignition and injection timing, idle speed, variable valve timing, valve control, revolutions limit, water temperature correction, transient fueling, gear control, and others.
Modern ECUs oftentimes use a microprocessor to process the sensor inputs from the engine in real time, and include the necessary hardware and software (or firmware) implementing all ECU functionality. The hardware typically includes electronic components, e.g. the CPU, on a printed circuit board, ceramic substrate or a thin laminate substrate. The software/firmware can be stored in the microcontroller/CPU or other integrated circuits situated on the circuit board(s), typically in some programmable or flash memory, allowing the CPU to be re-programmed by uploading updated code. In some instances reprogramming is achieved by replacing some of the memory chips, though this has become significantly less common in the past fifteen years. Advanced ECUs can receive inputs from various sources, and control other parts of the engine, while communicating with transmission control units or directly interfacing with electronically-controlled automatic transmissions, traction control systems, and the like. Communication between these devices is oftentimes achieved through a specialized automotive network called Controller Area Network (CAN). Modern ECUs often include features such as cruise control, transmission control, anti-skid brake control, anti-theft control, etc.
ECUs are used to control passenger car engines, which are most common, as well as industrial engines, which may not be quite as common. Semi-trucks, busses, construction equipment, generators, ships, etc. are usually built around large diesel engines. These engines vary from one (1) to sixteen (16) cylinders depending on the application with the most common being six (6) cylinders, although engines with greater than sixteen cylinders do exist, but they are rare. Electronic engine controllers first appeared in the 1960s (Bosch D-Jetronic) as pure analog devices. By 1981, every GM car in the US had an electronic ECU with an 8-bit processor. ECU control of industrial diesel engines lagged behind because the engines did not have to meet tough emissions standards. However, starting in the mid 1990s, emission regulations were imposed, which required electronic controls. The number of actuators to control, and the complexity of the controller (ECU) increased with each round of regulation, as the automotive electronics industry matured.
Companies such as Drivven have traditionally manufactured “research engine controllers”, which are typically used in the early development stages of new concept engines, as opposed to standard engine controllers that are used to control operational engines, for example in automobiles. Many of these ECUs are built using National Instruments (NI) controller hardware and LabVIEW™ software. In addition, there exist a large number of I/O modules specific to various different engines. Overall, traditional modular engine controllers and a typical production controller may differ from each other, as production controllers tend to be purpose built for a specific engine type and injector configuration. In order to minimize cost and engine controller requirements from concept to operation, it would be desirable to have ECUs that are as generic and flexible as possible.
Other corresponding issues related to the prior art will become apparent to one skilled in the art after comparing such prior art with the present invention as described herein.